Session: DA-08-01 Developments in FFS Techniques

Paper Number: 106332

106332 - Evaluation of the Api 579-1/asme Ffs-1 Kssccl1 and Kssccl2 Stress Intensity Factors 

The API 579-1/ASME FFS-1 2021 Fitness-For-Service stress intensity factor solution for a sphere with a surface crack, 360 Degrees, through-wall fourth order polynomial stress distribution (KSSCCL2) was independently investigated in this work. Axisymmetric, linear elastic finite element models of cracked spheres subjected to various applied stress fields were created and assessed. The objective was to estimate stress intensity factors (K) to evaluate crack-like flaws in spherical geometries using a parametric approach. The results were then used to calibrate the respective influence coefficient values (G_i). The sphere with a surface crack, 360 Degrees, internal pressure (KSSCCL1) uses the same table of influence coefficient values (G_i) and thus the new coefficients are also relevant to the KSSCCL1 scenario. A comparison of the newly calculated influence coefficient values to the existing values shows reasonable agreement for thin wall spheres with low ratios of internal radius to wall thickness (R_i/t). However, there is increasing discrepancy as the wall ratio increases, with the large differences predicted at R_i/t = 1000. The new influence coefficient values are recommended as an improvement for fitness for service assessments investigating 360-degree surface flaws in spherical geometries subject to fourth order polynomial through-wall stress fields (KSSCCL2) or internal pressure (KSSCCL1).

Presenting Author: Melanie Sarzynski Wiss, Janney, Elstner Associates, Inc.

Presenting Author Biography: Dr. Melanie Sarzynski is a Senior Associate at WJE Associates in Houston, TX where she leads a variety of engineering projects in the process industry. She has extensive experience in solid mechanics including evaluation of various failure modes to support design and FFS assessments. Her specialization in FEA, fatigue, and fracture mechanics has led to frequent consulting on the design and analysis of a variety of components, design certification of high pressure vessels, and strength and fatigue verification. Melanie is a licensed professional engineer, and received her BS, MS, and doctorate all in mechanical engineering from Texas A&M University.

Authors:

Steven Altstadt Wiss, Janney, Elstner Associates, Inc.
Melanie Sarzynski Wiss, Janney, Elstner Associates, Inc.